In Episode 10 of Countdown titled "The Muzzle Pile," the task force led by Nathan Blythe is reunited to solve a new mission in season 1. Secret Service agent Ryan Fitzgerald, aka Fitz, is burdened with several low-priority cases referred to as Muzzle Pile. Amidst this, he notices a suspicious voice note from a woman named Patricia Perez. She mentions something about a remote cabin where strange activities are afoot.
When Fitz investigates, he ends up finding out that Perez has been murdered. The evidence he found in the cabin hinted at some national implications, making this an urgent case. He realises the gravity and brings back the task force, including Meachum, Bell, Shepherd, and Finau, to form a new unit called "Armour". This is how the team, headed by Nathan, reunites for the new mission in episode 10 of Countdown.
Here is the new mission that reunites Nathan Blythe's task force in Countdown Episode 10.
Episode 10 leaps 10 months into the future, where the newcomer Fitz is complaining about not getting promoted all this time and also mentions something about the Muzzle Pile. He finds an email with a voice note from a woman. As mentioned, Perez's voice message about a remote cabin sparks some curiosity in Fitz, who, when further investigating the cabin, discovers Perez to be dead and a cache full of guns, cryptic map drawings, a manifesto, and some burnt photographs of the president of the United States. This makes the case high-profile and urgent, uniting Nathan Blythe's task force.
The objective of the mission is two-fold. One to solve the murder mystery of Patricia Perez, and second to assess the credibility of the threat against both the Governor of California and the president himself.
The team eventually also discovers a hidden basement beneath the cabin, which serves as a meticulously crafted shooting range. This suggests that the plot is well planned, organised and sinister.
Nathan Blythe joins his task force for another national-level terror plot in Countdown

In episode 10, Blythe returns home to Caty and Jordan while the team is coming together to investigate the Perez's murder case. This shows what's ahead for the character as Nathan now just wants to focus on being a good husband and father, removing his stone-faced task force commander mask.
After 10 months, some things have shifted within the team as Shepherd has been transferred to Washington, DC, forcing a separation with Bell. Fonau, on the other hand, has been promoted to sergeant, transforming his character from a family-first cop to a promising leader.
Meachum finally faces his medical condition by joining a clinical trial, and Oliveras steps into a more intimate, supportive role. The entire force shows up on his first operation, and this keeps up the major family theme of Countdown alive.
Therefore, this episode feels like a turning point and the start of something bigger, darker, and more serialised.